*{
  margin:0px;
  padding: 0px;
  background-color: #f5f5f5;
}
#layout{
  display: flex;
  flex-direction: column;
  width: 100%;/*移动端*/
  margin: 0 auto;
}
#top{
  width: 100%;
  background-color: yellow;
  flex:0 0 50px;
  /* height: 50px; */
}
#main{
  flex: 0 0 100%;
  display: flex;
  flex-wrap: wrap;/*移动端*/
}
#main ul:first-child{
  flex: 0 0 100%; /*移动端导航以换行的方式实现上下*/
  background-color: #f5f5f5;
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  border-left: 1px solid #fff;
  border-right: 1px solid #fff;
  align-items: flex-start;/*移动端*/
}
#main ul:first-child li {
  flex: 0 0 30%; /*没有显示效果*/
  height: 40px;
  line-height: 40px;
  text-align: center;
  border-bottom: 1px solid #fff;
}
#main ul:nth-child(2){
  flex: 0 0 100%;
  background-color: #f5f5f5;
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  justify-content: space-around;
}
#main ul:nth-child(2) li{
  flex: 0 0 30%;
  height: 120px;
  text-align: center;
  border-bottom: 1px solid #fff;
}